Water Demand Forecast Uncertainty

This paper examines the effect of water demand forecast uncertainty on the operation of a city's water supply system. It is based on a number of years experience the author has had in research and implementation of water demand forecast models, principally in Texas and California. The paper includes some general reflections on the nature of forecast uncertainty and a discussion of water system operations in the City of Austin, Texas, where a demand forecasting model has been used for several years to help manage the City's water system during peak demand periods. The variable being forecast is the combined pumpage of a city's water treatment plants. The time scale of the forecasts ranges from daily forecasts for one or two weeks ahead up to monthly forecasts for a year to eighteen months ahead, which is the main time scale over which demand forecasts can have an influence on system operations.